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Short description

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Reference 1:http:// www.physics.info/shock/

A shockwave is the high pressure wave produced by an object that travels faster than the speed of sound according to the same medium characteristics, in which different changes can be measured for example; extreme pressure and rising of the temperature.

The visualisation of the shockwave can be seen in the following picture.

History

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Reference 2:

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historia por francisto.....

www.nasa/...2.pdf

Rankine, was the first relevant figure who developed the theory, he makes his main contribution in his 1870 paper on the thermodynamic theory of waves published in the Philosophical Transactions of the Royal Society of London.

- He begins with: “The object of the present investigation is to determine the relations which must exist between the laws of the elasticity of any substance, whether gaseous, liquid, or solid, and those of the wave-like propagation of a finite longitudinal disturbance in that substance.”

- Later he writes: “It is to be observed, in the first place, that no substance yet known fulfills the condition expressed by the equation Image Added, between finite limits of disturbance, at a constant temperature, nor in a permanency of type may be possible in a wave of longitudinal disturbance there must be both change of temperature and conduction of heat during the disturbance”.

Therefore, Rankine by explaining that the shock transition is a non-adiabatic process, where the particles exchange heat with each other, but no heat is received from the outside, resolved the objections that had been raised by Rayleigh and others concerning the conservation of energy.

He goes on to find, for a perfect gas, the jump conditions for a shock wave moving with speed a into an undisturbed medium with pressure and specific volume defined respectively by P and S.

Shockwave

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Definition:As an object moves through a gas, the gas molecules are deflected around the object. If the speed of the object is much less than the speed of sound of the gas, the density of the gas remains constant and the flow of gas can be described by conserving momentum and energy. As the speed of the object increases towards the speed of sound, we must consider compressibility effects on the gas. The density of the gas varies locally as the gas is compressed by the object

Applications:

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Extracorporeal Extracorporeal shock wave lithotripsy (ESWL) is one of the well-known applications of shock waves. In addition to this success, , shock waves are applied to treat cancer, orthopaedic surgery in recent years. In brain neuro-surgery a revasculariztion of cerebral thrombosis is going to be established. Many interesting problems remained unresolved and its further improvements are required in order to achieve successful clinical applications

Why Shock wave happens:

When the speed of a source exceeds the speed of sound (v > c) the wave fronts lag behind the source in a cone-shaped region with the source at the vertex. The edge of the cone forms a supersonic wave front with an unusual large amplitude called a "shock wave". When a shock wave reaches an observer a "sonic boom" is heard.

Unlike ordinary sound waves, the speed of a shock wave varies with its amplitude. The speed of a shock wave is always greater than the speed of sound in the fluid and decreases as the amplitude of the wave decreases. When the shock wave speed equals the normal speed, the shock wave dies and is reduced to an ordinary sound wave.

Reference 3: www.nasa..../machang.html

In case that:

C = speed Speed of sound
V = speed Speed of the moving object
M = Mach number , would (Would be M)

So if an object move twice time faster that sound speed the Mach number would 2. |

When an object travels slower than sound, the ratio in this equation is greater than one, and the equation does not have a real solution. Traveling at the speed of sound makes the ratio equal one and results in a Mach angle of ninet¥y ninety degrees. Above the speed of sound, the ratio is less than one and the Mach angle is less than ninety degrees. The faster the object moves, the narrower the cone of high pressure behind it becomes. Measuring the vertex¥ vertex angle is a way to determine the speed of a supersonic object.

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Reference 4: 3 screenshot Screenshots from the video bellow Video below.

Mach Number

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This number was proposed by the Austrian phycisist and philosofer Ernst Mach in (1838-1916), one of the most notorius teorist phisicist.
The mach number is known as a measurement or unit and is defined as the coeficient of the velocity of an object and the velocity of the sound.

This number is used to express the velocity of an object taking the sound velocity as a reference, something very interesting about the moment is that velocity of sound changes depending on the atmospheric conditions.

For example: With a higher altitude compare to the sea level, the speed of sound is less than the one found at the sea level.

Video

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This video has been chosen because it explains briefly the main idea of shockwave and after watch the video you will have the main understanding of how, why and what is a shockwave.

I hope that all of you take 3 minutes to watch the video and enjoy the visual effects that a shockwave can generate.

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References

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Reference 1: http:

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//physics.info/shock/

Reference 2: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060047586_2006228914.pdf

Reference 3: http://videoswww.grc.howstuffworksnasa.comgov/discoveryWWW/29379-assignment-discovery-shock-wave-video.htmk-12/airplane/machang.html

Reference 4: Screenshot from the video bellow.

Reference 5: http://www.grc.nasa.gov/WWW/k-12/airplane/mach.html

Video 1: https://www.youtube.com/watch?v=gWGLAAYdbbc

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